Preparation:
1. In medium saucepan, melt the butter. Remove from heat; blend in the sour cream and flour to make a paste. Whisk in the milk and half-and-half and bring to a boil over medium heat, stirring frequently. Reduce heat to simmer, stir in salt, pepper, and cayenne, and stir frequently until the sauce thickens (about 5 minutes). Whisk in an additional tablespoon of Wondra® flour, if needed, for desired thickness.
2. Remove from heat, stir in shredded cheeses and stir well. Pour cheese into fondue pot or slow cooker set on HIGH. Serve with cubes of sourdough or French bread, or lightly cooked vegetables (broccoli or cauliflower florets work well).